Devices adapted for ultrasound location in patients and method of use

ABSTRACT

The present invention relates to devices including a plurality of voids that enhance visualization of the devices in a patient using ultrasound imaging. The sizes of the voids can vary to accommodate ultrasound devices having different ultrasound wave frequencies. The present invention is also directed to a method for using ultrasound imaging technology to detect the location of devices comprising a plurality of voids in a patient. An ultrasound device, such as a wireless, portable ultrasound device, may be used to propagate ultrasound waves towards the patient where the device is inserted. An ultrasound imaging device may then be used to generate an image of the device or a portion thereof from which the location of the device in the patient can be determined.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to devices adapted forultrasound imaging. More specifically, the present invention relates todevices and methods for using ultrasound imaging for verification andmonitoring of the location of a device in a patient.

2. Description of the Related Technology

Many devices are inserted into the body of patients for facilitatingdiagnosis and treatment. The proper use and functioning of such devicesfrequently depends on accurate positioning of the device in the patient.Current methods for determining the position of devices in patientssuffer from disadvantages such as insufficient resolution to accuratelyidentify the device location, the use of harmful x-rays to obtainpositioning information and the lack of simple, portable devices thatcan be employed for device location in a patient.

For example, the endotracheal tube (ETT) is routinely used in intensivecare units, emergency rooms and other healthcare settings to restore andmaintain an adequate air flow into the lungs of a patient. In a typicalendotracheal intubation procedure, the distal end of the ETT is insertedinto the trachea of a patient, generally at a location midway betweenthe vocal folds and the carina. The proximal end is connected with aventilation unit to supply air to the lungs.

Ensuring that the ETT is at the right location in the airway is criticalfor the success of the endotracheal intubation procedure. Adverseeffects are serious if the ETT is at the a suboptimal location, rangingfrom filling the stomach with air and, therefore, not ventilating thelungs if the ETT is misplaced in the esophagus to ventilating only onelung if the ETT is placed too deeply into a bronchus. In instances whereonly one lung is ventilated, the ventilated lung may becomeoverdistended, causing barotrauma to the ventilated lung and atelectasisin the contralateral lung

The commonly used technology for determining the position of the ETT inthe airway of a patient after its placement is by X-ray imaging of thepatient's neck and chest. Although X-ray imaging can accurately locatethe ETT in airway of a patient, this methodology has a number ofdrawbacks. Namely, X-ray imaging does not enable real-time determinationof the location of the ETT. Moreover, the negative impact on the patientis significant, including unnecessary ionizing radiation exposure, aswell as unnecessary lifting and arranging of the patient for the X-rayimaging. The repeated exposures to ionizing radiation in the form ofX-rays may be harmful to small babies, especially neonates who are stilldeveloping and thus at risk for possible long-term adverse effects

The development of an ultrasound method for localizing the position ofan ETT within the airway will allow practitioners to check the positionof the ETT without using X-rays. In many patients, but particularly inneonates, the position of the tube needs to be frequently checked as theETT may shift without deliberate intervention and a slight shift, evenof a few millimeters, can lead to compromised respiratory function,especially in neonates. An ultrasound based device and method wouldobviate the need for most X-ray imaging thereby reducing exposure toionizing radiation which results from the current standard method.

The invention addresses the difficulty in locating and monitoringdevices such as an ETT using ultrasound imaging systems. Althoughultrasound techniques are noninvasive and can generate real time imagesof the device in the body, these images are generally poor in qualitybecause of the presence of air within the immediate vicinity of thedevice to be located, including its tip, causing relatively poor echoamplitude strength. Poor quality ultrasound images, especially the lowcontrast between the device and surrounding tissue, make it challengingto correctly locate the device in the patient's body from conventionalultrasound images.

Several prior art references have offered partial solutions to enhancethe quality of ultrasound images. U.S. Patent application no.2006/0081255, for example, describes a system using a vibrationmechanism coupled to the distal end of an ETT. By vibrating the ETT, itis possible to generate a slight phase shift in the frequency of thereflected ultrasound wave, which helps to improve the ultrasound imagingquality. This system, however, only permits identification of the ETT byvirtue of its vibration, which can be difficult to discern and may causeunnecessary trauma to a patient. Vibration is especially problematic foruse in neonates, because the tissue of a neonate is very fragile andvibration of the ETT may cause damage to the airway. In addition,vibration itself may cause shift of ETT to an undesirable location,since a shift of the ETT by a few millimeters may compromise respiratoryfunction for neonates.

Another option is the use of a cuff affixed to a distal portion of theexterior tube wall of an ETT for enhanced imaging of the cuff [Raphael,David et. al., “Ultrasound confirmation of endotracheal tube placement,”Journal of Clinical Ultrasound, Vol. 15, issue 7, pp. 459-462 (December2005)]. The cuff may be constructed as a saline filled balloon.Alternatively, the cuff may be configured as a spongy foam cuffcontaining air cells that are inflated after intubation to seal thetrachea. Because the cuff is large, the longitudinal profile of the cuffis generally easier to identify than the distal end of the ETT whenviewed by ultrasonic imaging. Furthermore, longitudinal movement of theETT facilitates visualization of the spongy foam cuff The image qualityof these cuffs, however, is limited and still requires interpretation bya trained eye to accurately identify the location of the ETT.Furthermore, it needs to be particularly emphasized that such cuffs arenot suitable for use in neonates for fear of causing trauma to theairway.

The viability of using ultrasound imaging to identify the position of anETT in neonates has also been evaluated. Slovis, T L, et. al.“Endotracheal tubes in neonates: sonographic positioning” Radiology,July vol. 160 no. 1 (July 1986), for example, relied on the motion of anETT in the airway of a neonate caused by quickly moving the tube backand forth to provide a limited means for locating the ETT. In Lingle,Peter Allen, “Sonographic verification of endotracheal tube position inneonates: A modified technique” Journal of Clinical Ultrasound, vol. 16,no. 8, (October 1988), the manubrium of an intubated neonate waspalpated and a standoff patch was positioned on the infant's neck andchest that functioned as a reference point for identifying the distaltip of an ETT. Both studies required movement of the ETT to enablelocation of the ETT and still produced poor ultrasound images thatrequired an ultrasound specialist to interpret the ultrasound images.This method is also highly undesirable for use in neonates sincevibration of the ETT may cause tissue damage to the relativelyvulnerable tissue of such neonates. Also, the quality of the ultrasoundimage generated in this manner is not sufficient to enable healthcareproviders lacking specialized training in ultrasound imaging to reliablyuse this technique to verify the location of the ETT.

The aforementioned ultrasound methods all generate relatively poorquality images of the ETT and surrounding tissue with little contrastbetween the ETT and the tissue. Using these methods, it is difficult todistinguish the ETT from the background, and thus trained personnel arerequired to interpret these images. Due to the poor quality of theseimages, however, even an ultrasound specialist may, in some cases, notbe able to accurately discern the exact location of the ETT.

In another application, contrast agent microbubbles have been used toenhance the quality of ultrasound images in a patient's circulatorysystem. U.S. Pat. No. 6,086,540, for example, describes a method ofinjecting a gas contrast agent that forms microbubbles into a patient'sblood stream for the purpose of analyzing cardiac circulation. Thesemicrobubbles reflect ultrasound waves that increase the contrast betweenthe blood and the surrounding tissues. These references, however, do notsuggest how to employ such microbubbles to visualize a device or usingmicrobubbles to locate and monitor the position of a device within apatient.

Current standard techniques for determining the position of an ETTtypically require multiple exposures to ionizing radiation in the formof X-rays. The radiation is especially harmful to neonates. The priorattempts to use ultrasound imaging techniques for locating the ETT arenot sufficiently safe for use in neonates or sufficiently reliable foruse by healthcare providers lacking specialized training in ultrasoundimaging. Therefore there is a need to develop an improved noninvasiveprocedure which does not employ ionizing radiation for locating and/ormonitoring the location of a device, such as an ETT as well as improveddevices that can be more clearly visualized by a healthcare providerusing ultrasound imaging.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a device thatincludes a plurality of voids located in the tube wall in an amountsufficient for locating the device in a patient using ultrasoundimaging.

In a second aspect, the present invention relates to a method of usingultrasound imaging to detect the location of a device having a pluralityof voids located therein in patient's body, including the steps of:propagating an ultrasound wave through a location in the patient wherethe device is inserted; receiving the reflected ultrasound wave;generating an ultrasound image and locating the device using theultrasound image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an endotracheal tube inserted into the airway ofa patient. The proximal end of the tube is connected to a ventilationunit.

FIG. 2 is a longitudinal cross-sectional view of an endotracheal tube inaccordance with a first embodiment of the present invention looking atthe tube in the same direction as in FIG. 1.

FIG. 3 is a longitudinal cross-sectional view of an endotracheal tube inaccordance with a second embodiment of the present invention looking atthe tube in the same direction as in FIG. 1.

FIG. 4 is a longitudinal cross-sectional view of an endotracheal tube inaccordance with a third embodiment of the present invention looking atthe tube in the same direction as in FIG. 1.

FIG. 5 is a longitudinal cross-sectional view of an endotracheal tube inaccordance with a fourth embodiment of the invention looking at the tubein the same direction as in FIG. 1.

FIG. 6 is a transverse cross-sectional view of the tube wall of FIG. 4along line A-A.

FIG. 7 is a transverse cross-sectional view of the tube wall of FIG. 5along line A-A.

FIG. 8 is a flow chart illustrating a method for locating the ETT of thepresent invention using ultrasound imaging.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

For illustrative purposes, the principles of the present invention aredescribed by referencing various exemplary embodiments. Although certainembodiments of the invention are specifically described herein, one ofordinary skill in the art will readily recognize that the sameprinciples are equally applicable to, and can be employed in othersystems and methods. Before explaining the disclosed embodiments of thepresent invention in detail, it is to be understood that the inventionis not limited in its application to the details of any particularembodiment shown. Additionally, the terminology used herein is for thepurpose of description and not of limitation. Furthermore, althoughcertain methods are described with reference to steps that are presentedherein in a certain order, in many instances, these steps may beperformed in any order as may be appreciated by one skilled in the art;the novel method is therefore not limited to the particular arrangementof steps disclosed herein.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural references unless thecontext clearly dictates otherwise. Thus, for example, reference to “acontrast agent” may include a plurality of contrast agents andequivalents thereof known to those skilled in the art, and so forth. Aswell, the terms “a” (or “an”), “one or more” and “at least one” can beused interchangeably herein. It is also to be noted that the terms“comprising”, “including”, “composed of” and “having” can be usedinterchangeably.

For purposes of the present invention, the term “void,” as used herein,refers to voids or spaces of the same or different volumes locatedwithin a substrate, such as an endotracheal tube wall. These voids maybe arbitrarily shaped, though in some embodiments, use of particularsizes may be desirable to further improve imaging.

As used herein, “contrast agent” refers to any medium, including liquidsand gases that is echogenic, e.g. capable of enhancing the echo of apropagated ultrasound wave relative to an echo provided by tissue.

The present invention is directed to novel devices and methods forlocating such devices in a patient using ultrasound imaging. Preferably,the method of location of the device can be carried out in real time.The devices of the present invention allow use of ultrasound imaging toidentify, locate and monitor the devices in a patient using ultrasoundimaging. This is accomplished by the incorporation of a plurality ofvoids in the device, which voids are suitable for visualization usingultrasound imaging.

One exemplary embodiment of the invention is an endotracheal tube (ETT)10 and method for locating the endotracheal tube in a patient usingultrasound imaging, preferably in real time. The current inventionenables the identification, location and ongoing monitoring of thelocation of an ETT 10 in the airway of a patient, especially a neonate,using ultrasound imaging. The incorporation of voids 4 in the tube wall3 of the ETT 10 is employed to enhance the ultrasound image of ETT 10 tomake it significantly easier to visualize. This improved ETT 10 allows ahealthcare provider who is not an ultrasound imaging specialist toquickly and accurately confirm the location the ETT 10 in a patient'sairway in real time.

Referring to FIG. 2, a plurality of voids 4 located within tube wall 3is provided in an amount which is sufficient to reflect ultrasound wavesso that voids 4 are clearly viewable relative to the background in anultrasound image. The reflection from the voids 4 as well as thereflection from the surfaces 6 and 7 of the ETT 10 make ETT 10 appearespecially bright in an ultrasound image. The voids 4 also sharpen thecontrast between ETT 10 and the tissue surrounding ETT 10. This isimportant because healthcare providers routinely use visual assessmentsof gray scale brightness to determine the location of an ETT 10 in anultrasound image. The sharpened contrast between the image of ETT 10 andthe surrounding tissue thus facilitates visualization of ETT 10 usingthis technique.

Voids 4 located in the tube wall 3 are preferably filled with ambientair since this is the natural result of a typical, inexpensivemanufacturing process. However, it is possible to fill voids 4 withother materials, such as other liquids, gases or solids which mayfunction as contrast agents 5 (shown in FIGS. 6-7)capable of enhancingthe contrast between the space occupied by voids 4 and surroundingtissue in an ultrasound image. The ultrasound image quality of ETT 10embedded with voids 4 may therefore be further improved relative to anultrasound image of a conventional ETT through use of contrast agents,if desired. Any contrast agent capable of reflecting an ultrasound waveand enhancing the contrast between voids 4 and its surroundingenvironment is within the scope of this invention. Exemplary contrastagents may include air, inert gases, such as nitrogen, perfluorocarbons,such as perfluorobutane, perfluoropropane and perfluorohexane andcombinations thereof Air is a useful contrast agent.

Voids 4 positioned within tube wall 3 may be arbitrarily shaped and havethe same or different volumes. For example, the shape of voids 4 may bedictated by the manufacturing process used to fabricate ETT 10 withvoids 4 therein for the purpose of minimizing the cost of manufacture ofthe device. In exemplary embodiments, the voids 4 may be spherical orelliptical. The volume of the voids may vary and can optionally betailored for specific applications depending on the material used tofabricate ETT 10, as well as for the frequency of the ultrasound thatwill be used for imaging, if desired. The average diameter or largestdimension of the voids ranges from about 0.1 up to about 1000micrometers, preferably from about 0.3 micrometer up to about 50micrometers or 0.4 micrometer to about 10 micrometers.

As shown in FIGS. 2-3, voids 4 are preferably configured asmicrospheres. The size of voids 4 may be correlated to the frequency ofthe propagated ultrasound wave in order to enhance ultrasound imaging ofvoids 4. Voids 4 of various sizes therefore may be incorporated in tubewall 3 of ETT 10 and the size of voids 4 may be selected to optimizeechogenicity depending on the frequency of the ultrasound to be employedfor imaging. This allows for customization of ETT 10 for particularultrasound imaging devices by selection of a void size best suited foruse with a particular ultrasound device.

Voids 4 may also be substantially uniform in size. As shown in FIGS. 2,4, and 6, voids 4 have substantially the same shape and size, e.g.substantially the same diameter or largest dimension. In anotherembodiment, two or more voids 4 in tube wall 3 may have different sizes,as shown in FIGS. 3, 5 and 7, or three or more or a plurality of voids 4located within tube wall 3 may have different sizes. In an exemplaryembodiment, voids 4 are of mixed sizes between about 0.1 micrometer andabout 1000 micrometers. ETTs 10 having voids of different sizes arecapable of reflecting ultrasound waves over a wider frequency rangethereby enabling their use with different frequencies of ultrasound, ifneeded. The advantage of this embodiment of ETT 10 is that the same ETT10 can be used in conjunction with a variety of different ultrasounddevices, even if the devices do not produce ultrasound at the samefrequencies. Thus, ETTs 10 having varying sizes of voids 4 may besuitable for use in a larger set of circumstances and therefore reducethe cost of manufacturing and stocking different types of ETTs 10. Thisalso eliminates the possibility of using an ETT 10 with voids of anunsuitable size for the frequency emitted by a particular ultrasoundimaging device.

Referring to FIGS. 2 and 3, voids 4 may be uniformly or irregularlydistributed within the tube wall 3 and arranged in any pattern anddensity to enable visualization of voids 4 in the airway of a patientusing ultrasound imaging. In one embodiment, voids 4 are distributedthroughout the length of tube wall 3, extending from the proximal end 1to distal end 2 of the entire ETT 10. In another embodiment, voids 4 maybe positioned within a portion of tube wall 3 that is proximate to thedistal end 2, as shown in FIGS. 4-5.

This invention provides especially significant advantages for locatingan ETT 10 in neonates as it does not require additional components thatmay cause trauma to the airway of a neonate or which may potentiallyseparate from the body of the ETT 10 causing a choking hazard. Inaddition, neonates are very sensitive to slight shifts of the ETT 10 inthe airway, and therefore require frequent confirmation of the ETT's 10location. The current standard for determining the position of the ETT10 in neonates, use of X-rays, requires multiple exposures of theneonates to ionizing radiation and thus is undesirable.

The invention may be appropriately sized and scaled for use in neonates,adults or larger children. For neonates, ETT 10 may have a length ofabout 10 cm and inner diameter ranging from about 2.5 millimeters toabout 5 millimeters.

The present invention provides a number of advantages for identifying,locating and monitoring the position of ETT 10 within the airway of apatient. The device can minimize or eliminate the need for exposure toionizing radiation by obviating the need to use X-rays to locate ETT 10.The device also improves the ability to visualize ETT 10 in anultrasound image thereby allowing a larger universe of healthcareprovides to perform ETT 10 location procedures since specializedtraining in ultrasound imaging should not be necessary to interpret theimproved ultrasound images provided by the present invention. These sameadvantages can be realized for other devices that may be positioned inthe body.

The present invention can be implemented in a variety of devices. Otherexemplary devices which may include the same types of voids 4 andfeatures described in relation to the ETT may include, catheter devicessuch as venous catheters, dialysis catheters, and percutaneouslyinserted central catheters, feeding tubes such as nasogatric tubes,devices for use in brachytherapy which need to be positioned fortreatment, including expandable brachytherapy devices, and any otherdevices designed for insertion into the body where placement of thedevice is important for the use and/or functioning of the device.

In such devices, the voids 4 can be incorporated at any suitablelocation but are preferably incorporated in the device at key locationssuch as the tip of a catheter, the radiation delivery portion of abrachytherapy device, and the distal end of a feeding tube. The presentinvention is particularly suitable for devices that are placed in a bodycavity or a blood vessel. For example, in a catheter, the voids 4 can beincorporated at one or more locations in the catheter tube or wall.Similarly, in a feeding tube, the voids 4 can be incorporated at one ormore locations in the wall of the feeding tube. Other locations in suchdevices can also be employed as long as the user of the device candetermine proper positioning of the device in the body from theinformation obtained by ultrasound imaging of the portion of the devicewhich includes voids 4. In one embodiment, voids 4 are located proximateto a distal end of the device. In another embodiment, voids 4 arelocated along substantially the entire length of the device that isinserted into the body or patient to allow visualization of all or anyportion of the device using ultrasound imaging when the device islocated in a patient.

For brachytherapy devices, the voids 4 may be incorporated in anysuitable portion of the brachytherapy device. For example, in deviceswhich include tubes for delivery of radioactive materials to thetreatment area, voids 4 can be incorporation at a location in one ormore of such tubes which can be used for proper positioning of thebrachytherapy device for treatment, e.g. at the beginning and/or end ofthe portion of the tubes which will be located in the treatment area.Alternatively, voids 4 can be located in a portion of the brachytherapydevice which is at a fixed position relative to the treatment portion ofthe device. Though this embodiment is less preferred since it does notdirectly locate the treatment portion of the device in the body,indirect location can be employed using such devices. This may bedesirable, for example, when the device includes materials that mayinterfere with the ultrasound imaging.

Another significant advantage of the present invention is that it allowsthe provision of a truly portable (e.g. mobile phone size, includingbattery) ultrasound device which can include a dedicated imagingtransducer. Such a device is compatible for use in neonates, as well asolder children or adults, as required. The device would have asmall-footprint and minimal weight making it highly portable. Thisallows the device to be brought to the patient rather than requiring thepatient to be brought to the device making use of the device easier andallowing the device to be used by paramedics or at remote locations, asneeded.

The present invention also relates to a method of using ultrasoundimaging to detect the location of a device within a patient. This methodis illustrated by a description of a method for location of an ETT 10within an airway of a patient by visualizing voids 4 located within tubewall 3 of ETT 10. As described in FIG. 8, the method involves using anultrasound device 8 to propagate ultrasound waves towards the neck orchest of a patient where ETT 10 is located. The propagated ultrasoundwaves are reflected by the gas, such as air, or other contrast agentcontained in voids 4 of tube wall 3. These reflected ultrasound waves,e.g. ultrasound echoes, are received by ultrasound device 8 and anultrasound imaging apparatus 9, which is preferably part of ultrasounddevice 8 or directly connected thereto, is used to generate an image ofETT 10 and at least some of the surrounding tissue and thereby allow ahealthcare provider to locate ETT 10 within the patient. This method isalso applicable to other devices for insertion in the body.

Ultrasound device 8 can be any ultrasound device, preferably, anultrasound device of the latest generation. However, a portableultrasound device is most preferred since this provides mobility forhealthcare providers when they are trying to locate the device in apatient. This embodiment has the advantage of bring the ultrasounddevice to patients, instead of moving patients to the ultrasound device,because it may be undesirable, or even dangerous, to move the patient insome cases.

Wireless ultrasound devices 8 powered by batteries or another wirelesspower source, may be ideal for the present invention. Such wirelessportable ultrasound devices 8, though they normally generate images ofpoor quality, are sufficient to visualize the device of the presentinvention due to its improved echogenicity. The present inventiontherefore offers great freedom in terms of mobility to healthcareproviders and allows for real time imaging.

As discussed in above, the propagated ultrasound wave may have afrequency correlated to the size of the voids 4 to achieve enhancedechogenicity and improve visualization of the device. The method ofpresent invention may call for an ultrasound device 8 that propagatesultrasound waves having a frequency best suitable for the size of thevoids 4 in the device. For device having voids 4 of different sizes, asin FIGS. 2 and 4, the demand on ultrasound wave frequency is less, soultrasound devices 8 with different wave frequency may be suitable foruse. But for devices with voids 4 of approximately the same size, as inFIGS. 1 and 3, an ultrasound device 8 with a wave frequency mostsuitable for that particular void size is preferable. Therefore, fordevices with uniformly sized voids 4, an ultrasound device 8 capable ofemitting a correlated frequency is preferably selected. Alternatively, adevice having voids of a size correlated to ultrasound device 10 may beselected.

Preferred propagated ultrasound wave frequencies range from about 1 MHzto about 40 MHz, corresponding to void sizes of from about 66micrometers to about 0.16 micrometer in average diameter or largestdimension. In one embodiment, a mixture of frequencies ranging fromabout 1 MHz to about 40 MHz is employed in the propagated ultrasoundwave. In an exemplary embodiment, voids 4 may be most effectivelydetected by using ultrasound imaging frequency determined from thefollowing approximate expression: f[kHz]=6500/diameter of void inmicrometers. When ultrasound devices 8 with wave frequencies outside ofthat preferred range are used, the void size would also be outside thepreferred range, i.e. less than 0.16 micrometer or larger than 6.5micrometers and thus, it is possible to use voids 4 of, for example,about 0.1-1000 micrometers in average diameter or largest dimension. Theultrasound imaging quality can be enhanced by an appropriate combinationof ultrasound wave frequency, density and geometry of voids.

The present invention provides an improved method on locating an ETT 10in the airway of a patient. First, the echogenicity of voids 4 in thedevice enable a real time, noninvasive, reliable way of visualizing thedevice in the patient. The sharper contrast between the device andsurrounding tissue allows use of portable or wireless ultrasound devicesfor locating the device. This provides mobility to allow for use byparamedics or at the location of an accident or injury.

The present invention is especially useful in locating ETTs 10 inneonates. Because of the sensitivity of neonates, the small size of theairway in neonates and other safety concerns which significantlyincrease the need to locate and monitor the position of the ETT 10 inneonates, traditional methods of locating ETTs 10 in neonates are lessthan optimal for the reasons discussed above. With the enhanced contrastproduced by the voids 4, ultrasound devices including portable orwireless ultrasound devices, can be used to reliably visualize ETTs 10in neonates and obviate the need for invasive procedures or proceduresrelying on ionizing radiation.

It is to be understood that even though numerous characteristics andadvantages of the present invention have been set forth in the foregoingdescription, together with details of the structure and function of theinvention, the disclosure is illustrative only, and changes may be madein detail, especially in matters of shape, size and arrangement of partswithin the principles of the invention to the full extent indicated bythe broad general meaning of the terms in which the appended claims areexpressed.

1. A device comprising: a plurality of voids located in at least aportion of the device, wherein a number of said voids is sufficient forvisualizing the device in a patient using ultrasound imaging.
 2. Thedevice of claim 1, wherein the device is sized for use in neonates. 3.The device of claim 1, wherein the voids are a plurality of differentsizes.
 4. The device of claim 1, wherein the voids are located in aportion of the device proximate to the distal end.
 5. The device ofclaim 1, wherein the average diameter or largest dimension of said voidsis up to about 1000 micrometers.
 6. The device of claim 5, wherein theaverage diameter or largest dimension of said voids is from about 0.1micrometer to about 1000 micrometers.
 7. The device of claim 6, whereinthe average diameter or largest dimension of the voids is from about 0.3micrometer to about 50 micrometers.
 8. The device of claim 6, whereinthe average diameter or largest dimension of the voids is from about 0.4micrometer to about 10 micrometers.
 9. The device of claim 1, furthercomprising a contrast agent located in the voids, wherein said contrastagent is selected from the group consisting of air, nitrogen,perfluorobutane, perfluoropropane, perfluorohexane and combinationsthereof.
 10. The device of claim 1, wherein all of said voids aresubstantially the same size.
 11. The device of claim 1, wherein saidvoids are located along substantially the length of the portion of thedevice that is inserted into a patient.
 12. The device of claim 9,wherein said contrast agent is air.
 13. The device of claim 1, whereinthe device is selected from the group consisting of endotracheal tubes,catheters, feeding tubes and brachytherapy devices.
 14. A method forlocating a device in a patient comprising the steps of: inserting intothe patient a device having a plurality of voids located in at least aportion of the device, propagating ultrasound towards the patient,receiving an ultrasound echo from at least some of the voids and atleast some surrounding tissue of the patient, and creating an ultrasoundimage of the at least some of the voids and at least a portion of thesurrounding tissue of the patient from said ultrasound echo, anddetermining the location of the device in the patient from saidultrasound image.
 15. The method of claim 14, wherein a portableultrasound imaging device is used to propagate the ultrasound waves andreceive the ultrasound echo.
 16. (canceled)
 17. The method in claim 14,wherein the propagated ultrasound waves comprise a mixture offrequencies in the range of about 1 MHz to about 40 MHz.
 18. (canceled)19. The method of claim 14, wherein all of the voids are substantiallythe same size.
 20. The method of claim 14, wherein the voids are aplurality of different sizes.
 21. The method of claim 14, wherein a sizeof the voids is selected based on a frequency of the propagatedultrasound wave.
 22. The method of claim 14, wherein the device isselected from the group consisting of endotracheal tubes, catheters,feeding tubes and brachytherapy devices.